Internal combustion engines may use an exhaust driven compressor or turbocharger assembly to increase the manifold air pressure or MAP, thereby providing increased engine performance for a given engine displacement. A typical turbocharger assembly includes a turbine assembly in fluid communication with the exhaust gases and a compressor assembly in fluid communication with the inlet gases. A portion of the energy contained within the exhaust gases operate to spin or rotate a turbine wheel disposed within the turbine assembly. The turbine wheel is connected to a compressor impeller, disposed within the compressor assembly, through a common shaft. As such, the turbine wheel and compressor impeller rotate unitarily. In operation, as the exhaust gases rotate the turbine wheel, the rotating compressor impeller inducts or draws intake gases into the compressor assembly where it is pressurized for subsequent introduction to the internal combustion engine.
Recent advances in turbocharger design have led to the introduction of so-called variable geometry turbochargers. The variable geometry turbocharger typically includes a plurality of movable vanes disposed in one or both of the compressor assembly and turbine assembly, which operate to vary the operating characteristics of the turbocharger. Such variable geometry turbochargers may be effective in reducing so-called “turbo lag” in addition to improving the operating efficiency of the turbocharger assembly over a range of engine speeds. The accumulation of deposits, such as hydrocarbons and soluble organic fraction on the internal aerodynamic surfaces of the compressor housing and/or turbine housing may reduce the efficiency of the turbocharger and possibly cause sticking of the movable vanes contained therein.